This week, an utterly human response from a CEO to his employee who was taking time off to cope with mental-health issues took the Internet by storm. It prompted thousands of retweets, garnered dozens of headlines and even inspired a call-out from Sheryl Sandberg: “We need more leaders who encourage employees to bring their whole selves to work,” wrote the Facebook COO.

For those who missed it, a web developer named Madalyn Parker, who has written that she suffers from anxiety and depression, wrote an email to her colleagues saying she’d be out for a couple of days to “focus on my mental health.”

When the CEO responds to your out of the office email about taking sick leave for mental health and reaffirms your decision. 💯 pic.twitter.com/6BvJVCJJFq

Her CEO, Ben Congleton, replied by thanking her, saying every time she sends an email like that “I use it as a reminder of the importance of using sick days for mental health” and “you are an example to us all, and help us cut through the stigma.” Parker then shared it on social media, where it racked up hundreds of responses. (“OMG. Are they hiring?” asked one user on Twitter.)

There are many reasons Parker’s email got such a visceral response. For one, people love reading stories about the generous bosses they wish they had — stories often get shared widely of CEOs who give away their stock, dole out generous across-the-board raises or offer particularly cushy benefits to their workers. Congleton’s email was rightfully called a “master class in leadership” for his willingness to recognize his employee’s needs and remind her colleagues to do the same.

“When the CEO responds to your out of the office email about taking sick leave for mental health and reaffirms your decision, ” Rose tweeted.

“Many people wish they lived in the kind of world that these emails represent,” said Mary Killeen, a senior research associate at Syracuse University’s Burton Blatt Institute, which focuses on disability research and policy. “People wish they could be open with their supervisor and colleagues about occasionally needing time off, not because they are physically ill, but because they are dealing with a personal issue or an emotional state that makes it impossible, temporarily, to do their work.”

Then, there’s how well we can all relate to the challenges of taking sick days. Many Americans, of course, don’t get sick leave. But those who do — even if they don’t worry about the stigma of mental illness — often don’t use all their time off, whether because of job insecurity, a crushing workload or an expectation to work even when people should be home in bed.

“People are talking about this a lot in the context of mental health, but perhaps an equally important point is that our culture around work in the U.S. may not be particularly healthy,” said David Mandell, director of the Center for Mental Health Policy and Services Research at the University of Pennsylvania.

Clearly, the response to the email also reveals how many people continue to cope with mental illness in the workplace. One in four people will experience a diagnosable mental illness in their lifetime. And a mountain of research has shown how much of a stigma exists for people grappling with the issue at work.

“I was very impressed and actually surprised by the extent of the viral pickup” of the story, said John Quelch, the dean of the business school at the University of Miami who until recently held joint posts at Harvard’s schools of business and public health. “I think it indicates there is an undercurrent of awareness in the population that this is an issue and it has not been addressed in a systematic way by most corporations.”

There is an undercurrent of awareness in the population that this is an issue and it has not been addressed in a systematic way by most corporations

Surveys by the American Psychological Association’s Center for Organizational Excellence show that less than half of Americans (44 percent) say they believe the climate in their organization supports well-being, and that nearly 20 percent of employees say the challenges of their jobs were harder to handle in the past month due to mental health issues such as depression or anxiety. For employers, says the center’s director, David Ballard, “the costs of untreated mental health issues, the lost productivity, is actually more costly than the treatment side because people are there at work but not functioning to full capacity.”

That issue, known as “presenteeism,” is one several mental health experts said Parker’s email also highlighted when she wrote that “hopefully, I’ll be back next week and refreshed and back to 100 percent.” Studies have shown that mental health issues such as depression and mental illnesses had the third-highest annual per-employee costs from lost productivity while at work, up there with arthritis, hypertension, allergy, headaches and diabetes.

Mandell notes that the estimated productivity cost to working while sick is far more than the costs businesses endure when people are out of work. “The stigma associated with mental health that causes people to bring those to work is actually a huge productivity drain,” he said.

Yet for many employees, taking sick days when they’re needing to deal with mental health illnesses doesn’t feel like an option. In some workplaces, they may have to provide a doctor’s note, which is much easier to do for a high fever than a panic attack. “Companies are very nervous about opening the Pandora’s Box on mental health and support because of unknown quantification of costs,” Quelch said. “Given the stigma, the path of least resistance is to not take the sick day.”

Still, many were encouraged to see the positive, viral response of Parker’s email and her CEO’s response. Ron Honberg, senior policy adviser for the National Alliance for Mental Illness, said he recalls the offensive newspaper cartoons and negative, viral response from two decades ago came after it became clear the Americans with Disabilities Act applied to mental health.

Indeed, he says, “mental health day” has emerged as a widely used term that can mean anything from needing a break from exhaustion and stress to dealing with a more serious mental illness. “People will take a day of sick leave due to a very bad cold and we know they’re going to recover and it probably isn’t going to be a chronic condition, and people take sick leave because they have chronic [physical] conditions,” he said. “The same standards should apply to mental health conditions.” As long as it’s not abused, he thinks the broad application of the term “mental health day” is okay. “‘The fact we’re using it so commonly, and without even thinking about it, maybe reflects progress.”